text: The aqueous solution in the classical reaction contains glucose, sodium hydroxide and methylene blue. In the first step an acyloin of glucose is formed. The next step is a redox reaction of the acyloin with methylene blue in which the glucose is oxidized to diketone in alkaline solution and methylene blue is reduced to colorless leucomethylene blue. If there is enough oxygen available (i.e., after shaking the bottle), leucomethylene blue is immediately re-oxidized to methylene blue and the blue color of the solution persists. However, when the solution is left to rest, the dissolved oxygen is gradually irreversibly consumed, and at the point where it has been completely exhausted, the glucose reduction of methylene blue proceeds unopposed and the color of the solution rapidly disappears. The reaction is first order in glucose, methylene blue and hydroxide ion and zero-order in oxygen. The process can be described as a pseudo first order reaction, and can be used to illustrate the changing concentrations of the reagents over the course of the reaction as the solution changes from blue back to colorless.
  The final glucose oxidation products besides sodium gluconate have been identified as -arabino-hexos-2-ulose (glucosone), the anion of -arabinonate after splitting off of a formate anion and arabinonic acid.